The present invention relates to worktables of the type providing rolling elements to support the workpiece for movement therealong and more particularly to novel ball insert units therefor.
In order to minimize the resistance to movement of a workpiece across the surface of a worktable, rotatable ball elements or the like have been provided in the surface of the worktable to support the work thereon. Generally, these rotatable elements comprise ball casters which are positioned in insert units which in turn are set into recesses formed in the supporting worktable surface. The insert units usually have a head which is supported on the surface of the top plate or table and a shaft which extends through the top plate or table and outwardly of the lower surface thereof. Generally, the outwardly extending shaft has a screw thread, and a nut or other fastening element is screwed onto the threaded shaft and tightened against the bottom surface of the table. In some instances, the fastening element is a safety ring, a set screw, or the like. However all of these generally require that the mechanic have access to the bottom surface of the table or plate to effect the necessary engagement.
Use of separate fastening elements to retain the unit in the table increases the cost because of the fabrication requirements and difficulties in effecting assembly. Moreover, when the fastening elements must be assembled to a portion of the unit projecting downwardly from the lower surface of the table, it is possible for the elements to become misplaced or lost at the time of assembly and disassembly.
Accordingly, it is an object of the present invention to provide a novel ball insert unit for worktables which is relatively simple in structure and which can be rapidly and easily inserted and securely fastened into the worktable surface from thereabove.
It is also an object to provide such a ball insert unit which is relatively economical to fabricate and which provides a relatively long lived unitary assembly.
Another object is to provide such a ball insert unit wherein resilient biasing forces are applied between the ball insert and the worktable to maintain the ball insert units securely positioned within the table against inadvertent disassembly.